This paper discusses our newly developed technology for making GaAs/InGaAs/GaAs Tetrahedral-Shaped Recess (TSR) quantum dots. The heterostructures were grown by low-pressure MOVPE in tetrahedral-shaped recesses created on a (111) B oriented GaAs substrate using anisotropic chemical etching. We examined these structures by using cathodoluminescence (CL) measurements, and observed lower energy emissions from the bottoms of, and higher energy emissions from the walls of the TSRs. This suggests carrier confinement at the bottoms with the lowest potential energy. We carried out microanlaysis of the structures by using TEM and EDX, and found an In-rich region that had grown vertically from the bottom of the TSR with a (111)B-like bond configuration. We also measured a smaller diamagnetic shift of the lower energy photoluminecscence (PL) peak in the structure. Based on these results, we have concluded that the quantum dots are formed at the bottoms of TSRs, mainly because of the dependence of InAs composition on the local crystalline structure in this system. We also studied the lateral distribution and vertical alignment of TSR quantum dots by CL and PL measurements respectively. The advantages of TSR quantum dot technology can be summarized as follows: (i) better control in dot positioning in the lateral direction, (ii) realization of dot sizes exceeding limitations posed by lithography, (iii) high uniformity of dot size, and (iv) vertical alignment of quantum dots.

Fabrication methods of novel silicon quantum wires and dots using anisotropic wet chemical etching and thermal oxidation are newly proposed. The method realizes fine Si quantum wires, which are fully surrounded by the thermal SiO2 without any defects. The wires are straight and the Si/SiO2 interfaces are fairly flat. The 10 nm width wires are confirmed by Transmitting Scanning Microscopy observation in minimum size. The fine quantum dots are also fabricated using this method. The characteristics of the wires are investigated and the current oscillations in variation with the gate voltage are observed in low temperature. We believe the origin of these oscillations arise from one-dimensional subband conduction.